How to have bone scaling only effective on one action?
As i understand, All of your actions didn't have any Scaling Keyframes, so when you scale your bone, it apply effect to all actions.
So, all you need to do is go to action editor and add Normal Scaling Keyframes to your action before you Cheat on your actions.  


Go to Dope Sheet, Select Ation Editor

Select Scaling in Active Keying set

Press I to add Normal Scaling Keyframe

Repeat to all of your actions